Encephalomyocarditis virus replication complexes that prefer nucleoside diphosphates as substrates for viral RNA synthesis.

Replication complexes (RC) containing endogenous viral RNA templates and the viral RNA polymerase were isolated from encephalomyocarditis (EMC) virus-infected Krebs II cells by two different procedures one of which included removal of the bulk of the associated proteins by treatment with 2 M LiCl. Replacement of one or all the four nucleoside triphosphate (NTP) substrates by corresponding nucleoside diphosphates (NDPs) did not eliminate the ability of the RC to synthesize viral RNA products. Moreover, the complexes were shown to accept as substrates even nucleoside monophosphates (NMPs), provided at least one NTP was present in the system. These results suggested that nucleotide kinases, NMP kinase and NDP kinase, were associated with the RC, and this suggestion was confirmed directly. The RC could be resolved, by sucrose gradient centrifugation, into distinct components that exhibited marked preference for either NDPs or NTPs as substrates for RNA synthesis. It is suggested that, in the NDP-preferring components, the NTP molecules generated by the built-in nucleotide kinase system are channeled directly to the vicinity of the replication fork.